Electron beam devices are known in which electrons are generated and accelerated in a vacuum tube to traverse a thin window for use outside the vacuum tube.
While a vacuum environment is beneficial for generating and accelerating electrons, it is also desirable that an electron window be thin to allow electrons to penetrate the window with minimal energy loss. The energy lost by an electron penetrating a window may be gained by the window as heat and in destruction of chemical bonds of the window material. The combined factors of a minimization of window thickness effected to enhance electron penetration of the window, a large pressure difference felt by the window due to the vacuum environment within the tube, and the destruction and heating caused by electrons penetrating the window can result in small holes or defects in the window that destroy the vacuum and wreck the tube.
For some applications, it is desirable to produce a broad beam of electrons. A challenge in producing such a device is that increasing the area of an electron window generally reduces the ability of that window to withstand large pressure differences.
An approach to solving this dilemma is to use materials in the window that are tough yet permeable to electrons, as taught by U.S. Pat. No. 4,468,282 to Neukermans. Neukermans teaches using polycrystalline substrates to grow long thin windows for printing applications.
In U.S. Pat. No. 3,788,892, Van Raalte et al. teach of producing a window across a long, narrow opening of an envelope and supporting that window with a rigid foraminous reinforcing member. Similarly, U.S. Pat. No. 3,611,418 to Uno discloses a large window having a mesh-like supporting section.
An object of the present invention is to provide an electron beam device having a broad beam.
Another object of the present invention is to provide an electron beam device that is capable of easy repair after a hole has developed in an electron window.